What is the performance of the 465QK engine knock sensor when it is broken?

What is engine super knocking.

Engine "super knocking", also known as low-speed premature ignition, is an abnormal combustion phenomenon unique to supercharged direct-injection gasoline engines. When the engine inhales the mixture of fuel vapor and air, in the process of compression, due to the mixture of low ignition point substances in the fuel, it will cause the gas mixture to automatically deflagrate before the ignition of the spark plug, forming a new ignition point, and the flame spreads outward at a speed several times higher than the normal combustion, so that the cylinder wall is affected and vibrates, which is called detonation. To put it simply, knocking is a manifestation of abnormal pressure in the combustion chamber caused by abnormal combustion.

A phenomenon when detonation occurs.

The engine will emit a crisp and discontinuous metal knocking sound when a slight knock occurs, while a continuous metal knocking sound will occur when the engine will have a continuous metal knocking sound during a severe and continuous knock, and the engine power will also be significantly reduced.

What are the causes of detonation?

1 The air-fuel ratio is incorrect, and the mixture is too dilute to increase the combustion temperature, thereby increasing the engine temperature.

2. The octane number of fuel is too low, the octane number is an indicator of anti-detonation, the higher the octane number, the stronger the anti-detonation, and the lower the conversely, it is easy to detonation.

3. The cleanliness of the fuel is insufficient, and some physical substances and chemical impurities contained in the fuel, including some aromatic substances, will cause spontaneous combustion and detonation during the compression process of the engine.

4. Excessive carbon deposition in the combustion chamber, due to the serious carbon deposition, the actual volume of the cylinder becomes smaller, the compression ratio increases, and at the same time, the carbon deposition in the high-temperature environment will always burn red due to the poor heat dissipation ability, so that the high-temperature compressed mixture is not only ignited by the sequential spark plug, but also randomly ignited by the high-temperature carbon deposition in the cylinder, resulting in detonation.

5. The engine temperature is too high, the engine is too hot in the environment, the inlet air temperature is too high, or the engine cooling water circulation is poor, which will cause the engine to detonate at high temperature.

6 The ignition angle is too early, so that the piston can gain power as soon as it enters the power stroke after the compression stroke is completed, it is usually ignited before the piston reaches the top dead center. Ignition too early will cause most of the oil and gas to burn when the piston is still compressing the stroke, and the unburned oil and gas will be subjected to great pressure and spontaneous combustion, resulting in detonation.

The methods to solve detonation are as follows.

1. Use fuel that conforms to the compression ratio of the engine.

2. Avoid "drag gear" driving.

3. Regularly clean the carbon deposits and fuel injectors in the oil circuit.

4. Avoid high temperatures: check the coolant water level regularly, check and change the engine oil regularly, avoid long-term intense driving, and monitor the water temperature frequently when driving in summer.

5. Appropriate selection of high-quality fuel additives. For example, fuel additives containing PNF stock solution can solve the problem of engine knocking to a certain extent.

Detect engine knocking to suppress the occurrence of knocking phenomena. When the engineer adjusts the knock sensor, the vibration pattern of the knock is written into the electronic control unit. If the knock sensor detects a vibration pattern, the ECU determines the engine knock and then delays the ignition advance angle.

Currently, advanced knock sensors can even tell which cylinder is knocking and delay the ignition advance angle of that cylinder separately. 

The knock sensor is mounted in the middle of the engine block. For example, a four-cylinder engine is installed between cylinders 2 and 3, or one between cylinders 1 and 2 and one between cylinders 3 and 4. It is used to measure engine shake and adjust the ignition advance angle in case of engine knocking.

Usually piezoelectric ceramics. When the engine vibrates, the ceramic inside is squeezed to produce an electrical signal. Because this electrical signal is very weak, the connecting wires of ordinary knock sensors are wrapped with shielded wires.

Knock sensors are AC signal generators, but they are very different from most other AC signal generators in cars. In addition to detecting the speed and position of rotating shafts like magnetoelectric crankshaft and camshaft position sensors, they also detect vibration or mechanical pressure. Unlike stators and magnetoresistors, they are typically piezoelectric devices.

They are made of special materials that can sense mechanical pressure or vibration (for example, when the engine starts knocking, it can generate alternating voltage).

Engine damage can occur due to premature ignition, poor exhaust gas recirculation, and engine knocking caused by low-quality fuel. The knock sensor provides a knock signal to the computer, prompting the computer to readjust the ignition timing to prevent further knocking. They actually act as "oxygen sensors" in the ignition timing feedback control loop.

The working principle of the knock sensor: when the engine vibrates or knocks the cylinder, the piezoelectric ceramic produces a voltage peak, and the greater the knock or vibration, the greater the peak. The engine control unit (ECU) processes the signals received by the detonation sensor, and if a detonation is determined, the ignition is postponed and the detonation continues.

When the engine control unit ECU does not receive the signal from the knock sensor, the ignition time is advanced to ensure the optimal output of the engine. Therefore, the purpose of using a knock sensor is to improve the dynamic performance of the engine without knocking.

The engine knock sensor is damaged, the first manifestation is that the fault light is lit, the second manifestation is not so obvious, can not be seen, when the engine detonation, the computer can not detect it, so that the engine is damaged prematurely.

Check in the order of operation of the repair manual. Dial down the ECU connector and measure the resistance between the shield and the ground, and the measured resistance is almost infinite (the reference value is 1m). Maji checked the wiring, and there was neither a short circuit nor a broken wire, and it was normal.

The only thing left is to check the knock sensor (with an oscilloscope). Connect the probe of the oscilloscope observer to the connection terminal of the knock sensor, and gently tap the engine cylinder wall with a small hammer to output the signal waveform after operation. The peak-peak voltage of the signal waveform is only about 350mV, while the peak-to-peak voltage of the signal waveform transmitted by the normal detonation sensor is about 800mV.

At this point, it can be judged that the knock sensor is faulty. By replacing the new knock sensor, after inspection and testing, all faults disappeared.

Hello, the knock sensor is faulty, you should go to the repair shop in time to replace the new sensor. There are several symptoms of a malfunctioning detonation sensor:

1. The failure of the detonation sensor will cause the engine to shake, produce noise, and the fault light will be lit, which will cause serious damage to the firmware in serious cases;

2. During engine operation, the engine will be detonated due to the influence of excessive ignition time advance (ignition advance angle), engine load, temperature and fuel quality;

3. During detonation, because the gas burns before the piston moves to the top dead center, it will produce noise and reduce the engine power, and damage the mechanical parts of the engine.

4. In order to prevent knocking, the knock sensor is an indispensable and important component, and the ignition advance time is adjusted through the electronic control system.

(1) Check whether the engine is obviously overheated for detonation, and if so, find out the cause first. (There are many related causes of engine overheating, pay attention to analysis).

2) Check if the engine knocks due to the failure of the ignition system.

If the ignition advance angle is too large, the mixture will burn too fast, resulting in engine knock combustion. The reasons for the excessive ignition advance angle are as follows: the crankshaft position sensor is installed in the wrong position (or loose), the timing belt is installed in the wrong tooth, the operation program of the power control module is faulty, the air intake detected by the air flow sensor is too small, and the detonation sensor is slow to respond.

3) Check if the pressure in the fuel system is too low.

If the pressure of the fuel system is too low, causing the mixture to be too thin, the combustion rate of the mixture will decrease, and the heat transferred through the cylinder wall to the coolant after the mixture is burned will increase, resulting in a high engine temperature. The engine temperature is too high, which is prone to detonation and combustion.

4) Check if the fuel is contaminated.

The lower the designation (i.e., octane number) of gasoline, the less resistant the gasoline is to knock off, and the more susceptible the engine is to detonation combustion when using this gasoline as fuel. In addition, if impurities are added to the gasoline with a relatively high grade, it will also cause the anti-knock ability of the gasoline to decrease.

5) Check whether the engine knocks due to the failure of the engine cooling system.

The actual working temperature of the engine is determined by the heat generated by the combustion of the mixture per unit time and the heat emitted by the heat dissipation system, if the cooling system is faulty, the former will be greater than the latter, the temperature of the engine will be higher and higher, and the tendency to detonation and combustion will be greater and greater.

6) Check if the pressure of the cylinder is too much.

If the pressure of the cylinder is too high, the combustion rate of the mixture increases, and the likelihood of detonation combustion in the engine increases. The reason for the excessive pressure of the cylinder is that the cylinder head, piston or cylinder gasket model is not the same as the working volume of the cylinder and the cylinder pressure.

7) Check whether there is too much carbon deposits in the combustion chamber of the engine.

If a large amount of carbon deposits accumulate in the cylinder, the hot spots formed by the carbon deposits may ignite the mixture in advance during the cylinder compression process, causing the pressure in the cylinder to suddenly increase during further compression, resulting in detonation and combustion. The causes of carbon deposition are as follows: the mixture is too concentrated, the ignition energy is relatively poor, the quality of gasoline is relatively poor, and the engine burns oil for some reason, etc., which can be checked separately.

8) Check if the EGR system is working properly.

If the exhaust gas recirculation system works within the working range, the system fails and cannot make the exhaust gas enter the cylinder to participate in the combustion, which will inevitably cause the combustion temperature of the mixture to rise, so that the engine will overheat and be prone to detonation combustion.

9) Check if the application and calorific value range of the spark plug are correct.

Hello! The 4-cylinder car has a knock sensor.

There are up to 2 knock sensors, and there is also 1 knock sensor.

Engine ignition cannot be corrected in time.

The torque output of the engine cannot be precisely controlled.

The function of the knock sensor is to provide the engine computer with a sensor of the engine knocking situation, if the ignition time is advanced, it will lead to engine detonation, the detonation sensor is broken, the engine computer can not accurately judge the engine detonation, then the computer can not correct the ignition time, resulting in abnormal engine working conditions.

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The knock sensor is generally not easy to break, check the plug or wiring, whether the screw is loose or too tight, if it is broken, it must be replaced. Hope it helps.

The VQ23 is an old Ethereal V6 engine, and the knock sensor is installed in the middle of the two cylinder heads, under the air intake pipe!